Water heater



FIG. 1 is a perspective view of a water heater according to our design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view therefor; and,

FIG. 6 is a top view thereof.

The bottom view is planar and unornamented. 

The ornamental design for a water heater, as shown and described. 